If it is possible to do it with Steam Goldberg, a fork of the previously mentioned program, Greenluma, a fork of the previously mentioned and/or any other software, whether one or several; someone and/or some people explain how in a way someone without computer knowledge can understand it?
Yeah, you’re correct the otavepo repo is gone, almost certainly because it is literally illegal software.
Generally speaking, you can’t host hacking tools that specifically compromise proprietary software on github.
(EDIT: For clarity, SteamOS may be open source, Proton may be open source… but Steam itself? Hahahahah, no.)
Anyway, yeah, the given instructions simply are impossible to follow, you’re not crazy.
You would have to somehow find this otavepo software elsewhere, if it exists elsewhere.
However, the main page of this also says it works with gbe_fork by DetanUp01, and that seems to be right here:
https://github.com/Detanup01/gbe_fork
… This main page of the Goldberg repo also says that the author is not responsible for anything bad that happens to your Steam account while using all this software.
… because this is indeed the kind of thing that could get your Steam Account totally banned, and could also potentially get you hardware banned.
You almost certainly do not want to use this.
Is… some Steam Achievements for a game you torrented… really worth potentially getting permabanned from Steam?